Disinfection of bacterially contaminated hydrophilic PVS impression materials.

PURPOSE: This study evaluated disinfection of bacterially contaminated hydrophilic polyvinylsiloxane (PVS) and polyether impressions. MATERIALS AND METHODS: Four light-bodied PVS (Examix, Genie, Take 1, Aquasil) and one polyether (Impregum) impression materials were evaluated using three disinfectants (EcoTru [EnviroSystems], ProSpray [Certol], and bleach [diluted 1:9]) as spray and immersion disinfections for 10-minute exposures. Pseudomonas aeruginosa ATCC 15442, Salmonella choleraesius ATCC 10708, and Staphylococcus aureus ATCC 6538 was the microbial challenge. Test specimens were prepared using aluminum molds with ten tapered cones. Mucin covered each cone, followed by 0.01 mL of each bacterium. Impressions were made using low viscosity impression material that was injected over the cones and filled custom trays. One-half of the impressions were spray disinfected, while the others underwent immersion disinfection. Trays that were contaminated but not disinfected served as positive controls, while those not bacterially contaminated or disinfected served as negative controls. The impressions were poured with Silky Rock Die Stone, and after setting, two cones were placed within a sterile capsule and triturated into powder. Four milliliters of TRIS buffer (0.05 M, pH 7.0) containing sodium thiosulfate (0.0055% w/v) were poured in each tube. After mixing, the solution was serially diluted and spread-plated onto selective agars. After incubation, colony counting occurred. RESULTS: No viable bacteria transferred to casts from either spray- or immersion-disinfected impressions. Negative controls produced no microbial colonies. Positive controls produced on average 3.35 × 10(5) bacterial cells. CONCLUSION: Results suggest the methods used could disinfect contaminated impression materials. Microbial transfer from nondisinfected impressions to cones approached 33.5%.

[Prevention of infection transmission in dental laboratories]. / Prevenirea transmiterii infectiei în laboratoarele de tehnica dentara din Iasi.

UNLABELLED: The professional activity in a dental laboratory is associated with a high risk for infection transmission through the manipulation of impressions and prostheses contaminated with patients' saliva and blood. AIM: To assess the compliance of dental technicians in lasi town dental laboratories with the methods used for preventing infection transmission in their practices. MATERIAL AND METHODS: This questionnaire-based survey included 61 dental technicians aged 22 to 58 years from 29 dental laboratories. The 17 questions were related to the protection equipment, air ventilation, and disinfection of surfaces, instruments, impressions, and prostheses. SPSS 14 system, Chi-Square test were used for data analysis, and the levels of statistical significance were set at p < 0.05. RESULTS: 90.2% of the subjects claim the need of prosthetic items disinfection upon arrival at the laboratory from the dental office (p < 0.05). The protection equipment is used by 49.1% of the dental technicians included in this survey (full equipment 18.0%, safety glasses 45.9%, mask 37.7%, rubber gloves 19.6%). 59.1% of the laboratories are provided with air ventilation, while surface disinfection is common practice in 85.2%. Of the study subjects 62.1% disinfect the impressions, 26.1% the final prosthesis, and 25.0% disinfect the interocclusal registrations (p < 0.05). CONCLUSIONS: Educational programs aimed at increasing dental technicians' awareness of infection control by adopting the most effective prevention measures are essential for reducing the incidence of technicians, dentists, and patients; exposure.

Evaluation of the antimicrobial activity and dimensional alterations of alginate impression disinfectants.

This paper offers a quantitative evaluation of the antimicrobial efficacy of eight different disinfection procedures for irreversible hydrocolloid impressions and the dimensional changes induced by them. Samples were collected immediately after impressions, after the disinfection procedures and over casts and analyzed for bacterial growth. Control, enzyme solutions, acetic acid and ultraviolet irradiation samples showed bacterial growth. Chlorhexidine and 1% sodium hypochlorite presented adequate antimicrobial activity, while 2% sodium hypochlorite solution showed the best results. Dimensional changes were similar to those of the controls in all the tested agents. The results indicated 2% hypochlorite was the most appropriate disinfectant tested.

In vitro investigation of the integration depth of oral fluids and disinfectants into alginate impressions.

THE OBJECTIVE: The objective of this work is to prove that oral cavity fluids diffuse into alginate mass of impressions. In addition, the information is presented on the subject that disinfectants used for alginate impressions disinfection not only diffuse into alginate mass but penetrate deeper than oral cavity fluids. MATERIALS AND METHODS OF THE STUDY: Three examination groups were formed for the research, the results of which evidenced how deeply oral cavity fluids and disinfectants 'Alpha Guard GF' and 'Orbis' could possibly diffuse into alginate impression material 'Kromopan 100'. In the first examination group ten impressions from the upper jaw dental arch and mucosa were taken, firstly colouring oral cavity fluids with a special colouring tablet MIRA-2-TON (Hager Werken). Cuts were randomly selected from impressions and scanned aiming to establish the depth of the coloured oral cavity fluid penetration. In the second and the third examination groups taken alginate impressions were accordingly soaked in 'Alpha Guard GF' and 'Orbis' with pigment and later randomly selected cuts were scanned in the same manner as in the first research group. RESULTS. The research results establish that coloured dental cavity fluids maximum diffuse into alginate impression is up to 540 microm with the presence of 95% of discolouring while disinfectants 'Alpha Guard GF' and 'Orbis' accordingly diffuse into alginate mass up to 710 microm and 870 microm with the presence of 95% of discolouring. CONCLUSIONS. The results obtained show that disinfectants using them according to the recommendations of a manufacturer, diffuse into alginate mass deeper than oral cavity fluids at the time of impressions taking.

An analysis of the persistent presence of opportunistic pathogens on patient-derived dental impressions and gypsum casts.

PURPOSE: This study aimed to assess the persistent presence of microorganisms on patient-derived dental impressions and gypsum casts, while highlighting important human pathogens such as Candida, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. MATERIALS AND METHODS: The practices and opinions regarding cross-infection control from 59 general dentists in Japan were obtained via a questionnaire. Alginate impressions were made from 56 patients. Using a brain heart infusion agar medium, impression and imprint cultures were carried out to visualize the microbial contamination on the surfaces of the impressions and gypsum casts, respectively. The colonies on the surfaces of the 30 impression cultures and 26 imprint cultures were collected by swabbing and then inoculated onto selective agar plates to detect streptococci, staphylococci, Candida, MRSA, and P aeruginosa. RESULTS: The questionnaire showed that only 54% of general dentists had a cross-infection policy in their dental clinics, and only 30% to 40% were aware of the possible persistence of MRSA or P aeruginosa on impressions and gypsum casts. The impression/imprint cultures grew a large number of visible bacterial colonies on all of impression/gypsum cast samples investigated. Selective agar cultures demonstrated the presence of streptococci (100, 100%), staphylococci (56.7, 65.4%), Candida (30, 46.2%), MRSA (26.7, 15.4%), and P aeruginosa (6.7, 7.7%) on the impressions and the gypsum casts, respectively. CONCLUSIONS: This investigation showed that patient-derived dental impressions and gypsum casts are contaminated with numerous microbes, including Candida, MRSA, and P aeruginosa, which are known pathogens responsible for nosocomial and/or life-threatening infection in the immunocompromised host.

Clinical evaluation of the efficacy of removing microorganisms to disinfect patient-derived dental impressions.

PURPOSE: Disinfection of dental impressions is an indispensable procedure for the control of cross-contamination; however, there is limited information on the efficacy of disinfection under clinical conditions. The objective of this study was to clinically evaluate the disinfection efficacy of commercially available agents in removing oral pathogens from patient-derived impressions. MATERIALS AND METHODS: Impressions from 54 patients were divided into groups and either left undisinfected or underwent 1 of 5 disinfection treatments: (1) 2% glutaraldehyde (GA), (2) 1% sodium hypochlorite (SH), (3) 0.25% benzalkonium chloride (BC), (4) 1 ppm ozonated water (OW), or (5) the Hygojet/MD520 system (HJ). An impression culture technique using a brain heart infusion agar medium was used to visualize the microbial contamination on the surface of the impression cultures. The persistent presence of oral pathogens on the impression cultures was examined using selective isolation agar plates. RESULTS: The isolation frequencies of streptococci, staphylococci, Candida, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa species from undisinfected impressions were 100%, 55.6%, 25.9%, 25.9% and 5.6%, respectively. Disinfection with HJ and BC removed the microorganisms with the greatest efficacy, followed by GA, SH, and OW. Potential bacterial contamination could be detected even after disinfection had been performed. Combined use of BC plus GA or SH removed oral pathogens almost completely from dental impressions. CONCLUSIONS: This investigation showed that potential contaminants are still present, even after general disinfection procedures. Therefore, either HJ or the combined use of BC with GA or SH is recommended for clinical and laboratory use.

Efficacy of high-level microwave disinfection of dental gypsum casts: the effects of number and weight of casts.

The aim of this study was to determine if the bactericidal effect of microwaving gypsum casts is maintained at maximum capacity of the oven (16 casts). Batches of 8 and 16 gypsum casts made from in vivo impressions were divided in half. One half of each cast was microwaved at 900 W for 5 minutes. The remaining halves were left untreated. When assessed for bacteriological growth, the median cfu/mL of the untreated casts was between 10(5) and 10(6) [corrected] while the microwaved casts showed a cfu/mL of 0, indicating that microwaving as described will disinfect gypsum casts even at maximum capacity of the oven.

Efficacy of various disinfecting agents on the reduction of bacteria from the surface of silicone and polyether impression materials.

The aim of the present study was to evaluate the effectiveness of different disinfectants on the reduction of two resistant bacteria from the surface of impression materials. Impressions were made of a sterile metal model of the edentulous maxillary arch which had been contaminated with Staphylococcus aureus and Enterecoccus faecalis. The impressions were cultured before and after disinfection with 0.525% sodium hypochlorite, Gludex and Mikrozid spray disinfectant. For each of the three impression materials and the two microorganisms, spray disinfectant was found to be less effective than either sodium hypochlorite or Gludex.

High-level microwave disinfection of dental gypsum casts.

PURPOSE: To test whether microwave oven irradiation can disinfect gypsum casts in compliance with current disinfection requirements, and to determine whether this procedure would be as effective as a validated method of chemical disinfection of impressions. MATERIALS AND METHODS: In 2 in vitro experiments, samples of 5 irreversible hydrocolloid impressions of a disinfected acrylic resin model were contaminated with suspensions of recommended test organisms Staphylococcus aureus and Pseudomonas aeruginosa, respectively. In 1 in vivo experiment, 10 impressions were made of 10 subjects. All impressions were poured and the resulting casts cut in 2 halves. One half of each cast was exposed to 5 minutes of irradiation in a microwave oven at 2,450 MHz and 900 W. The other halves were left untreated as controls. In a second in vivo experiment, 10 impressions were disinfected by immersion in a 0.07% solution of NaOCl at pH of about 10 for 3 minutes, and then poured. All casts were incubated aerobically in Bacto tryptic soy broth at 37 degrees C for 6 hours and assessed for bacterial growth by counting colony-forming units per milliliter (cfu/mL) of the culture. The results were analyzed using the Wilcoxon signed-rank test. RESULTS: Untreated gypsum casts showed cfu/mL counts with a median log value of 6, while microwave-irradiated ones had median cfu/mL counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/mL counts with a median log value of 4. CONCLUSION: Under the described conditions, microwave-irradiated gypsum casts satisfy current disinfection requirements, but gypsum casts poured from chemically disinfected impressions do not.

In vitro study of transmission of bacteria from contaminated metal models to stone models via impressions.

The purpose of this study was to determine the risk of microbiological transmission into the dental laboratory via impressions and dental stone models. Metal master models were contaminated with Bacillus subtilis and Streptococcus sanguis. Impressions in alginate, polyvinylsiloxane, and polyether were used, and models were cast in two brands of dental stone. Samples were taken from the impression surfaces before and after casting, and sections from the stone models were taken by a technique developed for this study. After incubation, the numbers of colonies were counted and the numbers of colony-forming units per milliliter were calculated. The reductions were statistically significant but considered to be clinically insignificant. The conclusion is that even after severe contamination, the risks to dental laboratory personnel are minimal. "Normal" hygienic procedures are recommended instead of disinfection.